1. Field of the Invention
The present invention relates to a digital camera, and more particularly to a digital camera including a display device which displays an image formed by an image pickup device such as CCD.
The invention relates to a digital camera having a plurality of photographing systems, and more particularly to a digital camera having a plurality of photographing systems which are independently constructed including a plurality of solid-state image pickup devices such as CCDs, and which have automatic focusing functions, respectively.
2. Description of the Related Art
In recent years, a large number of digital cameras have been distributed as imaging apparatuses each having a CCD image pickup device or the like which is capable of easy photographing. In its photographing operation, the digital camera reads charges corresponding to the quantity of light (through photoelectric conversion) every pixel by the CCD image pickup device or the like, and converts the charges into image data, whereupon it records a photographed image as the image data on a recording medium such as magnetic recording medium.
In the course from the formation of an image to the recording, the digital conversion process of the formed image, an image creation process for displaying the formed image and a recording process for recording the photographed image are respectively executed as principal processes every photographing frame.
Besides, the digital camera of this type has become capable of photographing a dynamic image, owing to the use of the CCD image pickup device or the like. It has been proposed to photograph a dynamic image, for example, in such a way that a plurality of lens units are arrayed in the direction of an optic axis, and that the respective lens units are driven to zoom in accordance with photographing optical systems changed over and selected, so as to form optical images on the CCD (refer to JP-A No. 10-262175).
Further, imaging apparatuses etc. each including a plurality of CCD image pickup devices have been proposed. By way of example, in a technique disclosed in JP-A No. 11-122536, it has been proposed to dispose a plurality of CCDs for black-and-white use and for color use or ones of different device sizes, and a control unit for driving the CCDs, to divide an optical signal from an optical lens and receive divided signals by the respective CCDs, and to execute a signal process by the control unit. In this technique, the CCDs for photographing are changed over in accordance with the situation of surroundings, whereby an image corresponding to the circumstances can be obtained.
The digital camera stated above includes a zoom lever, and has the zoom function of enlarging or reducing the image of a subject on the basis of the operation of the zoom lever. There has also been proposed a camera including two photographing systems, and two display units which correspond to the respective photographing systems and which display images obtained by the respective photographing systems.
With the prior-art digital camera, however, during telescopic photographing, only a subject to be photographed can be confirmed by an optical finder or a display device of liquid crystal or the like functioning as the optical finder, and the situation of surroundings cannot be confirmed. This poses, for example, the problem that the proceeding of a game is not noticed in sports photographing, so the photographing of a scoring scene or any accident is missed.
Besides, an autofocusing function in the prior art poses a problem in case of using a lens of short focal depth, such as zoom lens, and depending upon the reference position and focal position of the lens on the occasion of autofocusing. More specifically, as shown in FIG. 18 by way of example, when contrast at each lens position is calculated as the lens is moved in the direction of arrow A in FIG. 18 (as the lens is moved from the side of the longest focal distance), a distance which the lens is moved till the detection of the maximum value of the contrast becomes longer than in case of moving the lens in the opposite direction to the direction of the arrow A, so that a longer time is expended in searching for the focal position.
Besides, in the case of using a lens of short focal depth, such as zoom lens, it is common that a stepping motor for driving the focusing lens is driven at intervals of several steps, thereby to specify a rough focal position range (as rough search), whereupon the stepping motor is finely driven, thereby to search the specified rough focal position range for a focus. Even on this occasion, as in the above, there is the problem that, since a focus search range is extensive in the rough search, a distance which the lens is moved becomes long, so a long time is expended in searching for a focal position.
Besides, even when the digital camera has the autofocusing function, a user cannot know which range the image of a subject is automatically focused on the CCD in, if the image of the subject has been focused, and so forth.
Further, it is considered to furnish a camera with two photographing systems, and two display units which display images obtained by the respective imaging systems, in correspondence with these respective imaging systems, and to dispose zoom levers in correspondence with the respective imaging systems in case of widening or narrowing an image angle.
Besides, an autofocusing function in the prior art performs autofocusing in such a way that, as shown in FIG. 35 by way of example, the position of a lens focusing in a case where a photographing distance to a subject is the closest distance previously determined is set as an initial position, whereupon a lens position at which a contrast value becomes the maximum value is found as a focusing position as the lens is driven stepwise every predetermined distance L from the initial position to the position of the lens focusing in a case where the photographing distance to the subject is an infinite distance. Accordingly, there is the problem that, when the focusing position lies on an infinite distance side as shown in FIG. 35, a long time is expended on the detection of the focusing position. With a contrary setting at which the position of the lens focusing in a case where the photographing distance to the subject is the infinite distance is set as an initial position, a long time is expended on the detection of the focusing position when the focusing position lies on a closest distance side.